Herein the term fluid indicates a material other than a gas which is capable of flowing without retaining its physical shape and accordingly excludes firm solids which retain their shape when subjected to mild pressure. The term includes liquids or creams which may be aqueous or anhydrous and flowable particulate solids. In particular, the present invention is directed to dispensers of a liquid of low or intermediate viscosity.
One class of dispensers of cosmetic fluids, including in particular deodorants and antiperspirants is commonly called a roll-on dispenser or applicator. In such dispensers, a bottle or reservoir has an outlet aperture which is shaped to form a housing for a rotatable roller, commonly a ball. The roller is retained by the housing, having a fraction of its surface in fluid connection with the reservoir or bottle and a further fraction of its surface exposed outside the housing. In use, the roller can rotate within the housing, thereby conveying liquid from within the reservoir to outside the housing where it can be brought into contact with skin (or some other chosen surface). Although in some instances the housing is formed together with the reservoir or bottle, it can alternatively be formed as a separate unit which is attached to the bottle by a suitable means, such as co-operating screw threads, or more usually by snap fit co-operating moulded lateral beads on the respective contact surfaces of the housing and bottle, e.g. to assist manufacture and/or assembly of the dispenser.
Conventionally, roller housings also include one or more means to seal the dispenser and prevent liquid egress past the roller when a cap has been fitted. These sealing means can comprise an annular sealing ring located on the interior surface of the housing between the roller and the reservoir of the bottle onto which ring the roller is urged by axial pressure exerted by the cap, usually by an annular wall depending from the interior of the top of the cap that contacts the roller.
Although roll-on dispensers have been used or proposed for use for at least 50 years, little attention, if any, has been given in prior publications to the simultaneous counter-flow of liquid out of the dispenser and the inflow of air into the bottle reservoir through the relatively narrow annular space between the roller and the interior of the housing. One of the problems that has recently been identified comprises an unpredictable fluctuation in the dosage of a liquid by a cosmetic roll-on of conventional size. Without being bound to any particular theory or explanation, it is believed that the unpredictable fluctuations arise at least partly as a result of the intermittent creation and release of a partial vacuum in the reservoir or housing when liquid is withdrawn by the roller and deposited on skin. When the partial vacuum is formed, the roller tends to be brought into contact with or at least pulled towards the annular ring on the inner surface of the housing restricting the flow of liquid. Variations in the extent of the partial vacuum are possible. However, irrespective of the precise explanation for fluctuations, it would be desirable to provide a dispenser which ameliorated such fluctuations.
A liquid applicator with a sealing ring against which the balled is pressed by the cap is described in U.S. Pat. No. 5,810,495. However, there is no recognition in U.S. Pat. No. 5,810,495 of the problems of variable fluid flow within the housing variable product dispensation and consequently no attempt is made to cure or ameliorate such problems. Indeed, the patent discloses the use of a valve inward of the ball housing which could easily exacerbate flow problems.
It has also been proposed in a number of patent specifications relating to roller/roll-ball dispensers to incorporate within the roller/ball housing a sealing ring and/or an intermediate reservoir underneath the roller/ball. The latter is able to retain fluid whilst the dispenser is in an upright orientation, for example as described in GB 1115861, GB 2255052, GB 2268912A, DE 19827965A, DE 20119329A, DE 29914452, U.S. Pat. No. 3,075,230, U.S. Pat. No. 3,069,718, U.S. Pat. No. 3,111,703, U.S. Pat. No. 324,839, U.S. Pat. No. 6,155,736 and U.S. Pat. No. 6,179,505, amongst others. There is no recognition in such specifications of the problems of air/gas flow within the interior surface of the housing and, consequently, no attempt was made to cure or ameliorate such problems in the specifications. Indeed, the very presence of an intermediate reservoir with limited inlet area could easily exacerbate flow problems.
It is an object of the present invention to reduce liquid dose fluctuations from a roll-on liquid dispenser having a removable cap and in particular from dispensers comprising a sealing ring against which a rotating roller is pressed by fitting the cap.